Simple Amines Research Articles

Oxidation-induced and dimer-structured clusteroluminescence for simple emissive amine molecules: Mechanism of non-traditional intrinsic luminescence

Non-traditional intrinsic luminescence (NTIL) substances have received a lot of attention because of their unique fluorescence properties in recent years. However, the NTIL molecules actually do not contain any aromatic or extended π-systems, therefore the relationships between luminous structure and emissive mechanism are still extremely debatable. In view of the above problems, this paper used small molecular amines (mainly triethylamine, TEA), a basic representative of nitrogen-containing NTIL molecules, as a template to study the structure and mechanism of NTILs. By circular treatment of reflux/distillation, careful analysis of the structural characterization coupled with theoretical calculations, we demonstrated that the optical properties of TEA were strongly related to oxygen molecules. Particularly, our data indicated that oxygen molecules induced a weak hydrogen bond between TEA molecules to form a dimer structure, meanwhile, the robust TEA-dimer and oxygen molecules were through n-π electron delocalization space conjugated to form an N⋯O clusteroluminogens. This physical bonding and spatial conjugate fluorophore structure not only well explains: why such nitrogen-containing NTIL substances lack normal organic conjugate structures and exhibit abnormally bright fluorescence in the visible spectrum when exposed to oxygen molecules (a traditional organic fluorescent material quencher), but also has important implications for further elucidating some tissue biofluorescence from oxidative folding of proteins.

Group I Alkoxides and Amylates as Highly Efficient Silicon-Nitrogen Heterodehydrocoupling Precatalysts for the Synthesis of Aminosilanes.

Group I alkoxides are highly active precatalysts in the heterodehydrocoupling of silanes and amines to afford aminosilane products. The broadly soluble and commercially available KOt Amyl was utilized as the benchmark precatalyst for this transformation. Challenging substrates such as anilines were found to readily couple primary, secondary, and tertiary silanes in high conversions (>90 %) after only 2 h at 40 °C. Traditionally challenging silanes such as Ph3 SiH were also easily coupled to simple primary and secondary amines under mild conditions, with reactivity that rivals many rare earth and transition-metal catalysts for this transformation. Preliminary evidence suggests the formation of hypercoordinated intermediates, but radicals were detected under catalytic conditions, indicating a mechanism that is rare for Si-N bond formation.

Organic molecular gate in mordenite for deep removal of acetylene and carbon dioxide from ethylene under humid condition

Adsorption-based processes for the ternary separation of CO2/C2H2/C2H4 show great potential and attractiveness, but commercialization remains a challenge due to the lack of efficient adsorbents. In this study, organic amine-modified mordenite (MOR) was developed, serving not only as a goalkeeper to accurately control ostiole and diffusion channels but also increasing the resistance to the influence of water molecules. This modification significantly improved the CO2/C2H2/C2H4 separation performance compared to pristine MOR, as evidenced by experimental and simulation results. ETA-MOR achieved excellent results in the deep purification of C2H4 from ternary CO2/C2H2/C2H4 mixtures, even under high humidity conditions. Cycling breakthrough tests demonstrated that the synthesized ETA-MOR material exhibited exceptional separation and structural stability. The obtained adsorbents exhibited excellent separation performance, thereby validating the effectiveness and potential of simple amine modification on commercially viable zeolites for industrial light hydrocarbon adsorption.

Chemoselective synthesis of tertiary and secondary amines by reductive amination of aldehydes

A simple and efficient catalyst-free chemoselective reductive amination of primary amines and aldehydes to synthesis of tertiary and secondary amines with borane complex was developed. Primary amines are converted into tertiary and secondary amines in one pot reaction under mild condition with good functional group compatibility and It does not require any catalyst to participate in this reaction. The chemoselective control was achieved by switching the steric hindrance of borane complex. The strategy was successfully applied to synthetize Tetracaine (anaesthetic) and the potential mechanism was verified by isotope labeling experiments.

Pharmacokinetic and Toxicological Aspects of 1,3-Dimethylamylamine with Clinical and Forensic Relevance

1,3-dimethylamylamine (1,3-DMAA) is a simple straight-chain aliphatic sympathomimetic amine, which was used as a nasal decongestant between 1948 and 1983. It reappeared in both dietary supplements as a substitute for ephedrine, and in party pills as an alternative to 3,4-methylenedioxymethamphetamine and/or 1-benzylpiperazine, after these substances were banned. Following its introduction to the market, it became one of the most widely used stimulants, and several case reports started to raise concerns about the safety and adverse effects of 1,3-DMAA. As a result, many countries banned or restricted the sale of 1,3-DMAA. Nevertheless, despite the efforts of regulating agencies, it has been reported that 1,3-DMAA is still found in dietary supplements and has been identified in doping controls. Therefore, the objective of this work is to review both the clinical and forensic aspects of 1,3-DMAA.

Controllable molecular orientation at the interface and coordination with second hydration-sphere to enhance separation of Pt(IV) and Pd(II) in hydrochloric acid solutions: Mass transfer based separation and molecular dynamics

In conventional liquid-liquid extraction, Pt(IV) and Pd(II) chloride complex anions PtCl62− and PdCl42− in concentrated hydrochloric acid cannot be separated using simple amine extractants according to the ion association mechanism based on the thermodynamic difference in the interaction of their inner sphere coordinated chloride ions with protonated amine. This study exhibits a novel strategy for enhancing the separation of PtCl62− and PdCl42− anions using thin-layer organic membrane-based laminar flow (TOMLF) extraction by controlling the acidified primary amine N1923 (A-N1923) molecular orientation on the surface of concentrated hydrochloric acid with a laminar shear flow. Experiments revealed that the separation selectivity is primarily determined by the interaction of A-N1923 molecules with the outer sphere-bound water molecules around PtCl62− and PdCl42− anions, and is easily controlled by regulating the A-N1923 molecular orientation on the surface of laminar flow. It is a new phenomenon that has not been previously documented. The evolution of A-N1923 molecular orientation and complexation sites induced by laminar shear flow would result in a controllable spatial geometry recognition, therefore promoting or inhibiting the separation of PtCl62− and PdCl42− anions in concentrated hydrochloric acid. This work is expected to provide new insight into the development of hydration-sphere coordination strategies based upon shear-switch laminar flow for controllable host-guest molecule recognition at a flowing liquid-liquid interface.

Schottky barrier height engineering on MoS2 field-effect transistors using a polymer surface modifier on a contact electrode

Two-dimensional (2D) materials are highly sought after for their superior semiconducting properties, making them promising candidates for next-generation electronic and optoelectronic devices. Transition-metal dichalcogenides (TMDCs), such as molybdenum disulfide (MoS2) and tungsten diselenide (WSe2), are promising alternative 2D materials. However, the devices based on these materials experience performance deterioration due to the formation of a Schottky barrier between metal contacts and semiconducting TMDCs. Here, we performed experiments to reduce the Schottky barrier height of MoS2 field-effect transistors (FETs) by lowering the work function (Фm = Evacuum − EF,metal) of the contact metal. We chose polyethylenimine (PEI), a polymer containing simple aliphatic amine groups (–NH2), as a surface modifier of the Au (ФAu = 5.10 eV) contact metal. PEI is a well-known surface modifier that lowers the work function of various conductors such as metals and conducting polymers. Such surface modifiers have thus far been utilized in organic-based devices, including organic light-emitting diodes, organic solar cells, and organic thin-film transistors. In this study, we used the simple PEI coating to tune the work function of the contact electrodes of MoS2 FETs. The proposed method is rapid, easy to implement under ambient conditions, and effectively reduces the Schottky barrier height. We expect this simple and effective method to be widely used in large-area electronics and optoelectronics due to its numerous advantages.

Approaches and Considerations for the Investigation and Synthesis of N-Nitrosamine Drug Substance-Related Impurities (NDSRIs)

N-Nitrosamine risk assessment of pharmaceuticals has moved from an initial focus on the potential presence of known small-molecule N-nitrosamines such as N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in active substances toward the potential for generation of more complex nitrosamine drug substance-related impurities (NDSRIs) in drug products. While N-nitrosation of simple secondary amines is well-understood, more complex amines can undergo alternative reaction pathways that can be more challenging to predict. A number of such complex amines are known not to undergo N-nitrosation but are either unreactive or react by alternative pathways such as C-nitrosation or nitration to generate non-N-nitrosamine products. This article proposes a standard set of three orthogonal nitrosation forced degradation type reaction conditions that can be used to investigate the potential for generation of novel N-nitrosamines by nitrosation of complex amines. These complementary reaction conditions are considered to provide a thorough evaluation of the potential for N-nitrosamine formation from complex amines with respect to risk factors within pharmaceutical manufacturing. If, after investigation of nitrosation under the proposed conditions, formation and isolation of an N-nitrosamine is not possible, the resultant understanding of chemical reactivity and stability can be used to justify that the N-nitrosamine in question would not be expected to be generated from the complex amine in the drug substance or product. If an N-nitrosamine is formed under these reaction conditions, the information gained can be used as part of the risk assessment and also provides a starting point for the development of a process to synthesize a discrete sample for further testing. Additionally, synthetic and analytical considerations that should be taken into account during preparation of novel N-nitrosamines for use in analytical or toxicological studies are discussed.

Copper-Catalyzed Synthesis of α-Keto Amides from Sulfoxonium Ylides.

We here described a method to synthesize α-keto amides from simple sulfoxonium ylides and secondary amines under the catalysis of copper. This transformation involved a very simple and clean catalytic system, and the substrates could be extended to aryl, heteroaryl, and tert-butyl sulfoxonium ylides to give diversified α-keto amides with good yields. Additionally, the mechanistic studies indicated that the α-carbonyl aldehyde might be a key intermediate in the reaction system.

Intermolecular Dearomative 1,2-Amination/Carbonylation via Nucleophilic Addition of Simple Amines to Arene π-Bonds.

The incorporation of the privileged amino functionality is of paramount importance in organic synthesis. In contrast to the well-developed amination methods for alkenes, the dearomative amination of arenes is largely underexplored due to the inherently inert reactivity of arene π-bonds and selectivity challenges. Herein, we report an intermolecular dearomative aminofunctionalization via direct nucleophilic addition of simple amines to chromium-bound arenes. This multicomponent 1,2-amination/carbonylation reaction enables rapid access to complicated alicyclic compounds containing amino and amide functionalities from benzene derivatives under CO-gas-free conditions, which also represents the first application of nitrogen-based nucleophiles in η6-coordination-induced arene dearomatizations.

Electrosynthesis of methyl 2-ureidobenzoates via a C2–C3 bond cleavage of isatins

A facile and efficient ring opening of isatin has been achieved by electrochemical anodic oxidation directly at room temperature. The results show that a constant current electrolysis of isatins in an undivided cell affords both the ester group and the urea group simultaneously. This reaction opens a new avenue for the synthesis of methyl 2-ureidobenzoates, enriches the research on the reactions of isatins involving the cleavage of the C2–C3 bond and shows a good range of substrates for both isatin and simple organic amine in an acidic buffer solutions of HOAc and Cu(OAc)2. In addition, this electrochemical C2–C3 bond cleavage reaction could be scaled up.

Fluorosulfonamide-Directed Heteroarylation of Aliphatic C(sp3)-H Bonds.

Herein, we describe a formal dehydrogenative cross coupling of heterocycles with unactivated aliphatic amines. The resulting transformation enables the direct alkylation of common heterocycles by merging N-F-directed 1,5-HAT with Minisci chemistry, leading to predictable site selectivity. The reaction provides a direct route for the transformation of simple alkyl amines to value-added products under mild reaction conditions, making this an attractive option for C(sp3)-H heteroarylation.

Iridium-Catalyzed Enantioconvergent Borrowing Hydrogen Annulation of Racemic 1,4-Diols with Amines.

We present an enantioconvergent access to chiral N-heterocycles directly from simple racemic diols and primary amines, through a highly economical borrowing hydrogen annulation. The identification of a chiral amine-derived iridacycle catalyst was the key for achieving high efficiency and enantioselectivity in the one-step construction of two C-N bonds. This catalytic method enabled a rapid access to a wide range of diversely substituted enantioenriched pyrrolidines including key precursors to valuable drugs such as aticaprant and MSC 2530818.

Distal meta-alkenylation of formal amines enabled by catalytic use of hydrogen-bonding anionic ligands

•Distal C–H activation mediated by non-covalent interactions •Catalytic amount of anionic ligand induces H-bonding interaction with amides •H bonding enables Pd-catalyzed distal meta-activation •Amines with variable linker lengths are susceptible to this protocol Regioselective and site-selective functionalization of distal C–H bonds has remained a significant challenge over the last decades. Although covalently attached directing groups have been designed to help solve this puzzle, their profound impact on step economy significantly hinders the protocol’s applicability. Weak non-covalent interactions have been developed to overcome this, but they have mainly been explored with Ir catalysis. Herein, we aim to execute a Pd-catalyzed meta-selective C–H functionalization of simple amines by harnessing weak non-covalent interactions between an anionic ligand and neutral substrate. A catalytic amount of organic salt acts as a suitable ligand for efficient meta-selective C–H olefination. Experimental and computational studies suggest that site selectivity is governed by the key H-bonding interaction between an anionic donating ligand and neutral motifs. The protocol can be further extended to amines with variable linker lengths, outlining the versatility and applicability of our methodology, while utilizing only a catalytic amount of directing ligand for the transformation. Regioselective and site-selective functionalization of distal C–H bonds has remained a significant challenge over the last decades. Although covalently attached directing groups have been designed to help solve this puzzle, their profound impact on step economy significantly hinders the protocol’s applicability. Weak non-covalent interactions have been developed to overcome this, but they have mainly been explored with Ir catalysis. Herein, we aim to execute a Pd-catalyzed meta-selective C–H functionalization of simple amines by harnessing weak non-covalent interactions between an anionic ligand and neutral substrate. A catalytic amount of organic salt acts as a suitable ligand for efficient meta-selective C–H olefination. Experimental and computational studies suggest that site selectivity is governed by the key H-bonding interaction between an anionic donating ligand and neutral motifs. The protocol can be further extended to amines with variable linker lengths, outlining the versatility and applicability of our methodology, while utilizing only a catalytic amount of directing ligand for the transformation. Charge-controlled Pd catalysis enables the meta-C–H activation and olefination of arenesMondal et al.ChemJanuary 24, 2023In Briefvan Gemmeren and co-workers report a method that enables the meta-selective olefination of arenes on the basis of a charge-controlled Pd-catalyzed C–H activation. The method relies on charge-charge and charge-dipole interactions to achieve unconventional regioselectivities. Mechanistic investigations support this novel means of controlling regioselectivity in Pd-catalyzed C–H activation. A broad scope of functionalized benzyl ammonium products can be accessed, and these are shown to be valuable linchpins for further functionalization toward densely functionalized arenes with challenging substitution patterns. Full-Text PDF Open Access

Site-selective methylene C-H oxidation of an alkyl diamine enabled by supramolecular recognition using a bioinspired manganese catalyst.

Site-selective oxidation of aliphatic C-H bonds is a powerful synthetic tool because it enables rapid build-up of product complexity and diversity from simple precursors. Besides the poor reactivity of alkyl C-H bonds, the main challenge in this reaction consists in differentiating between the multiple similar sites present in most organic molecules. Herein, a manganese oxidation catalyst equipped with two 18-benzo-6-crown ether receptors has been employed in the oxidation of the long chain tetradecane-1,14-diamine. 1H-NMR studies evidence simultaneous binding of the two protonated amine moieties to the crown ether receptors. This recognition has been used to pursue site-selective oxidation of a methylenic site, using hydrogen peroxide as oxidant in the presence of carboxylic acids as co-ligands. Excellent site-selectivity towards the central methylenic sites (C6 and C7) is observed, overcoming selectivity parameters derived from polar deactivation by simple amine protonation and selectivity observed in the oxidation of related monoprotonated amines.

Syn- versus anti-carbopalladation of alkynes with organoborons: access to indoles symmetrically and unsymmetrically substituted on their 2,3-positions.

A palladium (II)-catalyzed borono-ortho-CH activation/amination cascade for the construction of two C-N bonds and one C-C bond in a single synthetic sequence is reported. This method proceeds through a formal syn-carbopalladation of alkynes with organoboron compounds, forming alkenyl palladium species, which are trapped by simple amines to provide highly substituted indoles. Remarkably, with an electron-rich arylboronic acid, the reaction proceeds through an unexpected anti-carbopalladation terminated by ortho-CH activation of diarylalkyne/amination reaction to provide an unsymmetrically substituted 2,3-diaryl indole instead. In the follow-up chemistry, we demonstrate that urea participates in this cascade to offer a variety of free NH-indoles.

Organocatalyzed Phospha-Michael Addition: A Highly Efficient Synthesis of Customized Bis(acyl)phosphane Oxide Photoinitiators.

Addition of the P-H bond in bis(mesitoyl)phosphine, HP(COMes)2 (BAPH), to a wide variety of activated carbon-carbon double bonds as acceptors was investigated. While this phospha-Michael addition does not proceed in the absence of an additive or catalyst, excellent results were obtained with stoichiometric basic potassium or caesium salts. Simple amine bases can be employed in catalytic amounts, and tetramethylguanidine (TMG) in particular is an outstanding catalyst that allows the preparation of bis(acyl)phosphines, R-P(COMes)2 , under very mild conditions in excellent yields after only a short time. All phosphines RP(COMes)2 can subsequently be oxidized to the corresponding bis(acyl)phosphane oxides, RPO(COMes)2 , a substance class belonging to the most potent photoinitiators for radical polymerizations known to date. Thus, a simple and highly atom economic method has been found that allows the preparation of a broad range of photoinitiators adapted to their specific field of application even on a large scale.

Illuminating the dark metabolome of Pseudo-nitzschia-microbiome associations.

The exchange of metabolites mediates algal and bacterial interactions that maintain ecosystem function. Yet, while thousands of metabolites are produced, only a few molecules have been identified in these associations. Using the ubiquitous microalgae Pseudo-nitzschia sp., as a model, we employed an untargeted metabolomics strategy to assign structural characteristics to the metabolites that distinguished specific diatom-microbiome associations. We cultured five species of Pseudo-nitzschia, including two species that produced the toxin domoic acid, and examined their microbiomes and metabolomes. A total of 4826 molecular features were detected by tandem mass spectrometry. Only 229 of these could be annotated using available mass spectral libraries, but by applying new in silico annotation tools, characterization was expanded to 2710 features. The metabolomes of the Pseudo-nitzschia-microbiome associations were distinct and distinguished by structurally diverse nitrogen compounds, ranging from simple amines and amides to cyclic compounds such as imidazoles, pyrrolidines and lactams. By illuminating the dark metabolomes, this study expands our capacity to discover new chemical targets that facilitate microbial partnerships and uncovers the chemical diversity that underpins algae-bacteria interactions.

Photoresponsive Dissipative Macrocycles Using Visible-Light-Switchable Azobenzenes.

Visible light can be used to shift dynamic covalent imine assemblies out of equilibrium. We studied a fluorinated azobenzene building block that reliably undergoes geometric isomerism upon irradiation. The building block was used in combination with two different amines, ethylenediamine and R,R-1,2-diaminocyclohexane, to create a library of imine macrocycles. Whereas the simple amine can be used to access a polymeric state and a defined bowl-shaped macrocycle, the chiral amine gives access to a rich network of macrocycles that undergo both isomerisation as well as interconversion between different macrocyclic species, thereby allowing for control over the number of monomers involved in the cyclo-oligomerization; 1 H- and 19 F-DOSY NMR, MALDI-MS measurements, and UV/Vis spectroscopy were used to study the processes.

On amine treated polyoxymethylene (POM) blends with low formaldehyde emission for metal injection moulding (MIM)

When polyoxymethylene (POM)—a common polymer used in metal injection moulding feedstock—is exposed to heat and oxygen during compounding, it can be easily decomposed, releasing undesired gaseous formaldehyde products. In order to reduce the formaldehyde emission from POM, amine treatment was performed. The effectiveness of propylamine at different concentrations and its role as a formaldehyde scavenger was studied via the UV–vis Spectrophotometry, Fourier Transform Infra-red, Thermogravimetric Analysis, Scanning Electron Microscopy, and melt flow index. The results proved that a simple amine, such as propylamine, is a promising candidate for scavenging formaldehyde in POM. It is also demonstrated that the best concentration of propylamine is 2 wt.% (POM-PA2) with a minimum formaldehyde emission of 1.44 mg/L. Further, when used in formulating metal injection moulding feedstock (MIM), the POM-PA2 reveals good rheological properties and high green strength. These advantages make the modified polyoxymethylene (POM-PA2) a promising binder system for MIM feedstock.